JP6914615B2 - Methods for manufacturing negative electrode materials for lithium-ion batteries, lithium-ion batteries, negative electrode materials for lithium-ion batteries, and their manufacturing equipment. - Google Patents

Description

The present invention relates to a negative electrode material for a lithium ion battery, a lithium ion battery, a method for manufacturing a negative electrode material for a lithium ion battery, and a manufacturing apparatus thereof.

Conventionally adopted lithium ion batteries use a binder material on the negative electrode side of the negative electrode active material (hereinafter, also referred to as “negative electrode material”) graphite (natural graphite, artificial graphite, etc.) and the negative electrode material. It has a negative electrode with a mixed mixture layer. _{Further, on the positive electrode side, a binder material (PVDF) is formed by bonding lithium (Li) oxide powder (LiCoO 2} , LiNiO ₂ , LiMnO _2, etc.) of the positive electrode material and the positive electrode active material and conductive graphite (mainly carbon black, etc.). : It has a positive electrode provided with a mixture layer formed by mixing with polyvinylidene fluoride, etc.). Further, the cell container of the lithium ion battery is filled with an electrolytic solution, and a separator (mainly a polyolefin-based porous material or a porous polypropylene sheet or the like) is provided between the negative electrode material and the positive electrode material. Has been done.

The above-mentioned separator is provided so as to allow the electrolytic solution to pass through and cause the movement of lithium ions, and to separate the electrodes so that an electrical short circuit does not occur.

Charging and discharging of a lithium ion battery is performed by moving lithium ions between a negative electrode material and a positive electrode material in an electrolytic solution. During charging, lithium ions move to the negative electrode side, and during discharging, lithium ions move to the positive electrode side. Charging is done through an externally connected power source and discharging is done through an externally connected resistor (load).

By the way, in the field of lithium ion batteries, in recent years, a technique of using silicon particles as a material in place of the above-mentioned graphite as the negative electrode active material has been disclosed. For example, as an example of silicon particles, a powder having a diameter of about 38 microns (μm) or less formed by crushing single crystal silicon in a mortar and classifying using a mesh is raised at 30 ° C./min in an argon atmosphere. Some are heated to 150 ° C. (reached temperature) at a temperature rate (see Patent Document 1). Further, as another example, by supplying liquid silicon tetrachloride into high-temperature and high-concentration zinc gas and reacting it at a high temperature of 1050 ° C. or higher, silicon tetrachloride is reduced to form silicon particles. After crystal growth and aggregation of fine silicon at 1000 ° C. or lower, particularly 500 to 800 ° C., the particle size of the formed silicon particles is adjusted and collected in an aqueous zinc chloride solution. It is disclosed that high-purity silicon particles having a particle size of about 1 to 100 μm can be obtained by this work, and that they can be used (see Patent Document 2).

Japanese Unexamined Patent Publication No. 2005-032733 Japanese Unexamined Patent Publication No. 2012-101998 International Publication No. WO2015 / 189926 Pamphlet International Publication No. WO2013 / 027686 Pamphlet

However, in the prior art, when silicon particles are used as the negative electrode material, the electric capacity in charging and discharging can be increased, but on the other hand, lithium is occluded and released into the silicon particles, and the volume of the silicon particles fluctuates. Or will be destroyed. As a result, there is a problem that the charge / discharge cycle characteristics cannot be maintained.

For example, in the case of the silicon particles disclosed in Patent Documents 1 and 2 described above, since it is necessary to perform a high temperature synthesis and collection process, the manufacturing process until the silicon particles as the negative electrode material are obtained becomes extremely complicated. As a result, it is inevitable that productivity will decrease and manufacturing costs will increase. Further, the technique disclosed in Patent Document 3 is effective in that some of the silicon particles are not electrically isolated due to expansion and contraction, for example, but there is still room for improvement. There is. That is, the development of lithium-ion batteries using silicon particles is still in progress.

Based on the above-mentioned technical problems, the inventors of the present application have sought to find a higher performance negative electrode material that can be applied to the mechanism of a lithium ion battery without limiting the material used as the negative electrode material to only silicon particles. Diligent research and analysis were repeated.

As a result, the inventors of the present application, in a peculiar aspect, take in a characteristic silicon fine particle into an internal space formed by using graphite, surround it and internalize it, so to speak, integrate or unite it. As a result (hereinafter, also referred to as "composite"), it was found that a higher performance negative electrode material can be realized in which the usefulness of the characteristic silicon fine particles is remarkably enhanced. The present invention was created based on the above viewpoint.

The present invention solves at least a part of various problems related to charge / discharge cycle characteristics and the like that a conventional negative electrode material using silicon particles has, and is expected to have an effect of reducing carbon dioxide gas. It greatly contributes to the realization of negative electrode materials for higher performance lithium-ion batteries and their manufacturing methods.

The negative electrode material of one lithium ion battery of the present invention is silicon fine particles having a volume distribution having a mode diameter and a median diameter of 30 nm or less and / or an aggregate or aggregate of the silicon fine particles, and at least multi-layer petals. It contains the agglomerates or aggregates in a shape or scaly fold, and graphite surrounds at least a part of the silicon fine particles and / or the agglomerates or the aggregates.

The above-mentioned negative electrode material is a composite of silicon fine particles and / or agglomerates or aggregates of the silicon fine particles in a state of being folded in a multi-layer petal shape or a scale shape, in which at least a part of the aggregates is surrounded by graphite. Includes. In addition, the silicon fine particles and / or the agglomerates or aggregates are very fine agglomerates or aggregates having a volume distribution with a mode diameter and a median diameter of 30 nm or less. Therefore, although the detailed mechanism is not yet clear, the silicon fine particles and / or the aggregate or the aggregate, coupled with the specificity of the multi-layer petal-like or scaly shape of the aggregate or the aggregate described above. By surrounding the object with graphite, the degree of freedom of the silicon fine particles and / or the agglomerates or the aggregate can be suppressed to some extent by the graphite and the silicon fine particles and / or the graphite and the agglomerates or This leads to enhanced cooperation with the aggregate. As a result, by adopting this negative electrode material, it is possible to realize a lithium ion battery in which the charge / discharge capacity does not change much even if charging / discharging is repeated, in other words, the charging / discharging cycle characteristics are good. Alternatively, an increase in charge / discharge capacity can be realized.

Further, in the apparatus for producing a negative electrode material of one lithium ion battery of the present invention, by crushing crystalline silicon, silicon fine particles having a mode diameter and a median diameter of 30 nm or less have a volume distribution and / or the silicon fine particles. Aggregates or aggregates of By enclosing at least a part of the object or the aggregate, a complex containing the above-mentioned graphite and the silicon fine particles, or a complex containing the graphite and the aggregate or the aggregate is formed. It is provided with a forming portion.

According to the equipment for producing the negative electrode material of this lithium ion battery, very fine silicon fine particles and / or agglomerates of the silicon fine particles having a volume distribution having a mode diameter and a median diameter of 30 nm or less are used depending on the crushed portion. Form an aggregate. Here, at least the aggregate or the aggregate in a state of being folded in a multi-layered petal shape or a scale shape is formed. In addition, the manufacturing apparatus comprises at least a part of the silicon fine particles and / or agglomerates or aggregates surrounded by graphite to form a composite containing the graphite and the silicon fine particles, or the graphite. It further comprises a complex forming portion that forms a complex containing the aggregate or the aggregate. Therefore, although the detailed mechanism is not yet clear, the silicon fine particles and / or the aggregate or the aggregate, coupled with the specificity of the multi-layer petal-like or scaly shape of the aggregate or the aggregate described above. By surrounding the object with graphite, the degree of freedom of the silicon fine particles and / or the agglomerates or the aggregate can be suppressed to some extent by the graphite and the silicon fine particles and / or the graphite and the agglomerates or This leads to enhanced cooperation with the aggregate. As a result, according to this manufacturing apparatus, the charge / discharge capacity does not change much even if charging / discharging is repeated, in other words, the negative electrode material of the lithium ion battery having good charging / discharging cycle characteristics, or the charging / discharging capacity can be increased. It can contribute to the production of negative electrode materials for lithium-ion batteries.

Further, in the method for producing a negative electrode material of one lithium ion battery of the present invention, by crushing crystalline silicon, silicon fine particles having a mode diameter and a median diameter of 30 nm or less have a volume distribution and / or the silicon fine particles. The pulverization step of forming the aggregate or aggregate in a state of being folded into at least multi-layer petals or scales, and the graphite is the silicon fine particles and / or the aggregate. Complex formation that encloses at least a part of an object or an aggregate to form a complex containing the graphite and the silicon fine particles, or a complex containing the graphite and the aggregate or the aggregate. Including the process.

According to the method for producing a negative electrode material of a lithium ion battery, very fine silicon fine particles and / or agglomerates of the silicon fine particles having a volume distribution having a mode diameter and a median diameter of 30 nm or less are formed by a pulverization step. Form an aggregate. Here, at least the aggregate or the aggregate in a state of being folded in a multi-layered petal shape or a scale shape is formed. In addition, in this production method, at least a part of the silicon fine particles and / or the aggregate or the aggregate is surrounded by graphite, so that the graphite and the composite containing the silicon fine particles, or the graphite thereof. It further comprises a complex forming step of forming a complex containing the aggregate or the aggregate. Therefore, although the detailed mechanism is not yet clear, the silicon fine particles and / or the aggregate or the aggregate, coupled with the specificity of the multi-layer petal-like or scaly shape of the aggregate or the aggregate described above. By surrounding the object with graphite, the degree of freedom of the silicon fine particles and / or the agglomerates or the aggregate can be suppressed to some extent by the graphite and the silicon fine particles and / or the graphite and the agglomerates or This leads to enhanced cooperation with the aggregate. As a result, according to this manufacturing apparatus, the charge / discharge capacity does not change much even if charging / discharging is repeated, in other words, the negative electrode material of the lithium ion battery having good charging / discharging cycle characteristics, or the charging / discharging capacity can be increased. It can contribute to the production of negative electrode materials for lithium-ion batteries.

By the way, the crystalline silicon in each of the above-mentioned inventions includes not only single crystal silicon but also polycrystalline silicon. Further, metallic silicon can be selected as the crystalline silicon in each of the above-mentioned inventions. It should be noted that the crystalline silicon of each of the above-mentioned inventions is, for example, silicon chips or silicon cutting chips or polishing chips that are usually regarded as waste in the silicon cutting process in the production process of a silicon wafer, which is a manufacturing cost. This is a very suitable mode from various viewpoints such as reduction of the amount of water, reduction of the load on the environment, and reuse of resources.

Therefore, from the viewpoints of reduction of manufacturing cost, ease of procurement of raw materials, reduction of environmental load, and / or resource utilization, etc., graphite contains crystalline silicon chips or cutting chips. A negative electrode material of a lithium ion battery that surrounds at least a part of the chips or cutting chips is also another aspect that can be adopted. Further, a lithium ion battery comprising a complex forming portion in which graphite surrounds at least a part of chips or cutting chips of crystalline silicon to form a composite containing the graphite and the chips or cutting chips. The device for producing the negative electrode material of the above is also another aspect that can be adopted. In addition, lithium ions include a complex forming step in which graphite encloses at least a portion of crystalline silicon chips or cutting chips to form a complex containing the graphite and the chips or cutting chips. A method for producing a negative electrode material for a battery is also another aspect that can be adopted.

Further, in each of the above-mentioned inventions, the above-mentioned aggregates or aggregates in a state of being folded in a multi-layered petal shape or a scale shape are more likely to store and release lithium ions with higher accuracy or more easily. In order to do so, it is possible to employ a negative electrode material of a lithium ion battery in which at least a part of the surface of the above-mentioned agglomerates or the above-mentioned aggregates, or the above-mentioned chips or the above-mentioned cutting chips is covered with carbon. Is a preferred embodiment of. From the viewpoint of easy storage or release of lithium ions, it forms carbon covering at least a part on the surface of the above-mentioned aggregates or the above-mentioned aggregates, or the above-mentioned chips or the above-mentioned cutting chips. It is another preferred embodiment to employ an apparatus for producing a negative electrode material of a lithium ion battery including a coating forming portion. Similarly, a method for producing a negative electrode material for a lithium ion battery comprising a coating forming step of forming carbon covering at least a part on the surface of the above-mentioned aggregate or the above-mentioned aggregate, or the above-mentioned chips or the above-mentioned cutting chips. Is another preferred embodiment.

Further, in each of the above-mentioned inventions, graphite, or more positively expressed as a so-called "layer" (for example, graphene or graphene sheet) of graphite, is the above-mentioned agglomerate having a very fine and peculiar shape. Surrounds the aggregate. However, the graphite does not necessarily completely enclose the silicon microparticles and / or the agglomerates or aggregates. Therefore, it can be said that the above-mentioned composite is surrounded by graphite rather than the aggregate or the aggregate contained in graphite.

According to the negative electrode material of one lithium-ion battery of the present invention, it is possible to realize a lithium-ion battery in which the charge / discharge capacity does not change much even if charging / discharging is repeated, in other words, the charging / discharging cycle characteristics are good. Alternatively, an increase in charge / discharge capacity can be realized. Further, according to the device for manufacturing the negative electrode material of one lithium ion battery of the present invention, the change in charge / discharge capacity is small even if charging / discharging is repeated, in other words, the negative electrode of a lithium ion battery having good charge / discharge cycle characteristics. It can contribute to the production of materials or negative electrode materials for lithium-ion batteries that can increase the charge / discharge capacity. In addition, according to one method for producing a negative electrode material for a lithium ion battery of the present invention, a lithium ion battery having a good charge / discharge cycle characteristic, in other words, has a small change in charge / discharge capacity even after repeated charge / discharge. It can contribute to the production of a negative electrode material or a negative electrode material of a lithium ion battery that can increase the charge / discharge capacity.

It is a flow chart which shows the manufacturing process of the negative electrode material of the lithium ion battery of 1st Embodiment. It is a schematic diagram which shows the manufacturing apparatus and manufacturing process of the negative electrode material of the lithium ion battery of 1st Embodiment. It is a figure which shows the TEM (transmission electron microscope) image of an example of silicon fine particles and / or aggregates or aggregates thereof which went through the coating formation step (S4) of 1st Embodiment. It is an SEM image of an example of silicon fine particles and / or aggregates or aggregates thereof of the first embodiment. It is an SEM image of an example of enlarged silicon fine particles and / or aggregates or aggregates thereof in the first embodiment. FIG. 5 is an SEM image of (a) another example of an aggregate or aggregate of silicon fine particles in the first embodiment, and (b) a partially enlarged view of (a). It is a figure which shows the TEM image of the silicon fine particle of 1st Embodiment. It is a graph which shows (a) the crystallite diameter distribution in the number distribution, and (b) the crystallite diameter distribution in the volume distribution with respect to the crystallite diameter of the silicon fine particles of the 1st Embodiment. It is a graph which shows the result ((a) wide range, (b) limited range) of the X-ray diffraction measurement of silicon fine particles and / or aggregates or aggregates thereof of 1st Embodiment. It is a schematic block diagram of the lithium ion battery of 2nd Embodiment. It is a schematic diagram which shows the manufacturing apparatus and manufacturing process of the negative electrode material of the lithium ion battery of another embodiment.

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this description, common reference numerals are given to common parts throughout the drawings unless otherwise specified. Further, in the figure, each of the elements of each embodiment is not necessarily shown while maintaining a scale ratio of each other. In addition, some reference numerals may be omitted in order to make each drawing easier to see.

<First Embodiment>
FIG. 1 is a flow chart showing a manufacturing process of a negative electrode material for the lithium ion battery of the present embodiment. Further, FIG. 2 is a schematic view showing a manufacturing apparatus and a manufacturing process of the negative electrode material of the lithium ion battery of the present embodiment.

The method for manufacturing a negative electrode material of a lithium ion battery of the present embodiment and the method for manufacturing a lithium ion battery provided with the negative electrode material are, for example, cutting silicon in the production process of a silicon wafer used for a semiconductor product such as a solar cell. Various processes using silicon chips or silicon cutting chips or polishing chips (hereinafter, also referred to as "silicon chips, etc." or "chips, etc."), which are usually regarded as waste, as an example of a starting material. To be equipped. In addition, chips and the like also include fine chips obtained by crushing a silicon wafer to be discarded by a known crusher. As shown in FIG. 1, the method for manufacturing the lithium ion battery of the present embodiment is the following steps (1), (2), (5), and (6), or the following steps (1) and (2). ), (4), (5), and (6). In addition, the method for manufacturing a lithium ion battery of the present embodiment can further include the following step (3) as another aspect that can be adopted.
(1) Cleaning step (S1)
(2) Crushing step (S2)
(3) Oxide film removing step (S3)
(4) Coating forming step (S4)
(5) Complex formation step (S5)
(6) Negative electrode forming step (S6)

Further, as shown in FIG. 2, the manufacturing apparatus 100 for the negative electrode material (or negative electrode) of the lithium ion battery of the present embodiment mainly includes a washing machine (cleaning and pre-crushing machine) 10, a crushing machine 20, and a dryer (not shown). (Not), rotary evaporator 40, silicon fine particles and / or agglomerates or aggregates thereof (hereinafter, also collectively referred to as “silicon fine particles, etc.”), a coating forming a carbon covering at least a part of the surface. Part 60, a composite forming part 70 that forms a composite containing graphite and silicon fine particles by surrounding at least a part of silicon fine particles and the like, and a part of a negative electrode forming step of a lithium ion battery. The mixing unit 80 is provided. Of the above configurations, the apparatus 100 for manufacturing the negative electrode material (or negative electrode) of the lithium ion battery, which does not include the coating forming portion 60, is another aspect that can be adopted.

Further, the apparatus 100 for manufacturing the negative electrode material (or the negative electrode) of the lithium ion battery of the present embodiment may include an oxide film removing tank 50 and a centrifuge 58 as another aspect that can be adopted. Only the above-mentioned crusher 20, or the washing machine 10 and the crusher 20 are referred to as a crushing unit in the present embodiment.

(1) Cleaning step (S1)
In the cleaning step (S1) of the present embodiment, for example, it is formed in the cutting process of single crystal or polycrystalline silicon, that is, a crystalline silicon mass or an ingot (n-type crystalline silicon mass or ingot). Silicon chips and the like are washed. A typical silicon chip or the like is a chip or the like in which a silicon ingot is machined by a known wire or the like (typically, a fixed abrasive wire). Therefore, in the present embodiment, silicon fine particles and the like constituting the negative electrode material of the lithium ion battery are formed by using silicon chips and the like, which have been conventionally regarded as waste materials, as a starting material, so that the manufacturing cost can be reduced. It is excellent in terms of ease of procurement of raw materials, reduction of environmental load, and / or resource utilization.

The cleaning step (S1) of the present embodiment is mainly aimed at removing organic substances adhering in the process of forming silicon chips and the like described above, and typically organic substances such as coolants and additives used in the cutting process. And. In the present embodiment, as shown in FIG. 2, first, the chips and the like 1 to be cleaned are weighed, and then the chips and the like 1, the predetermined first liquid, and the balls 11 have a bottomed cylindrical shape. It is introduced into the pot 13a. After sealing the inside of the pot 13a using the lid 13b, the two columnar rotating bodies 15 of the ball mill machine, which is the washing machine (cleaning and pre-crushing machine) 10, are rotated to rotate the rotating body 15 on the rotating body 15. Rotate the pot 13a. As a result, in the pot 13a, the chips and the like 1 to be cleaned are dispersed in the first liquid to perform the cleaning of the chips and the like 1 and the preliminary pulverization treatment.

Here, in the ball mill machine of the present embodiment, steel balls, porcelain balls, balls and the like are used as balls 11 (crushing medium) contained in the pot 13a and the lid 13b, and the pot 13a and the lid 13b are rotated. It is a crusher that gives a physical impact force. A preferred example of the first liquid described above is acetone. Further, in a more specific embodiment, for example, 300 ml (mL) of acetone is added to 100 g (g) of silicon chips or the like, and a ball mill machine (in this embodiment, manufactured by MASUDA Co., Ltd.) is added. Silicon chips and the like were dispersed in acetone by stirring in the pot 13a and the lid 13b placed on the rotating body 15 of Universal BALL MILL) for about 1 hour. The ball types of the ball mill machine were alumina balls having a particle size of φ10 mm (mm) and alumina balls having a particle size of φ20 mm. In the cleaning step (S1) of the present embodiment, the dispersion treatment is performed by pre-grinding and stirring silicon chips and the like in the first liquid in the ball mill machine. Therefore, since the cleaning efficiency is remarkably improved as compared with the treatment of simply immersing in the first liquid, silicon particles suitable for improving the negative electrode characteristics of the lithium ion battery, particularly the charge / discharge cycle characteristics, can be used. It becomes possible to obtain.

After the cleaning step (S1), the lid 13b is opened to discharge the silicon particles together with the first liquid, and then the first liquid is removed by suction filtration by a known vacuum filtration means to become a waste liquid. On the other hand, the remaining silicon particles are dried in a known dryer. If necessary, the silicon particles obtained after the drying treatment are pre-crushed and washed again in the washing machine (washing and pre-crushing machine) 10 by the same step. An example of another cleaning method that can be adopted in the cleaning step (S1) is cleaning using the RCA cleaning method or cleaning using water (including pure water).

(2) Crushing step (S2)
After that, in the pulverization step (S2), a predetermined second liquid is added to the washed silicon particles, and the silicon particles are pulverized in the bead mill machine. Therefore, in the present embodiment, the silicon particles that have undergone the cleaning step (S1) are further finely crushed by the bead mill machine used after the above-mentioned ball mill machine, in other words, after the crushing by the above-mentioned ball mill machine. Become.

A preferred example of the second liquid of this embodiment is IPA (isopropyl alcohol). As a pretreatment of the crushing step, the second liquid and the silicon particles obtained in the washing step (S1) are placed in the pot 13a so that the weight ratio of the second liquid is 95% and the silicon particles are 5%. After storing, the pre-crushing process is performed by rotating the pot 13a and the lid 13b of the washing machine (washing and pre-crushing machine) 10. After the relatively coarse particles are removed by passing the slurry containing the pre-ground silicon particles through a mesh having an opening of 180 microns, the obtained slurry containing the silicon particles is subjected to a bead mill of the crusher 20 (the present embodiment). In the above, further fine pulverization treatment is performed using a star mill LMZ015) manufactured by Ashizawa Fineting Co., Ltd. More specifically, a slurry containing silicon chips from which silicon chips having a particle size of 180 microns or more have been removed is charged into the introduction port 21 of the crusher 20 and finely pulverized by the crusher 20 or the same. After the treatment, it leads to the filter 25 on the discharge port 24 side. If the fine pulverization is insufficient by this treatment, the slurry is returned to the introduction port 21 side of the crusher 20 by using the pump 28 and circulated so that the fine pulverization treatment can be performed again. Processing can also be performed. An example of a specific bead type of a bead mill machine is zirconia beads having a particle size of φ0.5 mm. After recovering the slurry containing the finely pulverized silicon particles, the second liquid is removed by using the rotary evaporator 40 that automatically performs vacuum distillation, so that the finely pulverized silicon particles and the like are produced. can get.

In the present embodiment, about 450 g of zirconia beads having a particle size of φ0.5 mm are introduced, and the fine pulverization treatment is performed at a rotation speed of 2900 rpm for 4 hours to obtain silicon fine particles and the like. Further, in the crushing step (S2), it is also adopted that the crushing process is performed by any one of the crushers consisting of a ball mill, a bead mill, a jet mill, and a group of shock wave crushers other than the above, or a combination of two or more kinds. It is another aspect that can be done. Further, as the crusher used in the crushing step (S2), not only an automatic crusher but also a manual crusher may be adopted. However, from the viewpoint of forming agglomerates or aggregates of silicon fine particles in a state of being folded into multi-layer petals or scales, which will be described later with high accuracy, a crushing step (S2) consisting of treatment with a bead mill, or It is preferable that the pulverization step (S2) including the treatment with a bead mill is adopted.

Further, using a known raikai machine (as a typical raikai machine, manufactured by Ishikawa Factory Co., Ltd., model 20D type), the silicon fine particles and the like obtained in the above-mentioned crushing step (S2) are further crushed. Is another preferred embodiment that can be adopted. Since this crushing treatment improves the dispersibility when forming the negative electrode of the lithium ion battery, it is possible to obtain the effect of preventing or suppressing the destruction of the negative electrode by the occlusion / release of lithium with high accuracy. ..

(3) Oxide film removing step (S3)
In the present embodiment, the oxide film removing step (S3) is performed as a preferred embodiment. However, even if this oxide film removing step (S3) is not performed, at least a part of the effects of the present embodiment can be achieved.

In the oxide film removing step (S3) of the present embodiment, a treatment is performed in which the silicon fine particles and the like 2 obtained in the pulverization step (S2) are brought into contact with hydrofluoric acid or an aqueous solution of ammonium fluoride. The silicon fine particles and the like 2 obtained in the pulverization step (S2) are dispersed by immersing them in an aqueous solution of hydrofluoric acid or ammonium fluoride. Specifically, in the oxide film removing tank 50, the silicon fine particles and the like 2 are dispersed in the hydrofluoric acid or ammonium fluoride aqueous solution 55 using a stirrer 57 to oxidize the surface of the silicon fine particles and the like 2. Objects (mainly silicon oxide) are removed.

After that, the centrifuge 58 separates the silicon fine particles or the like from which some or all of the oxides on the surface have been removed from the hydrofluoric acid aqueous solution. Then, silicon fine particles and the like are immersed in a third liquid such as an ethanol solution. By removing the third liquid, silicon fine particles or the like from which a part or all of the initially formed surface oxide (or oxide film) has been removed can be obtained. When the oxides that may exist on the surface of the silicon fine particles and the like 2 are not removed, the silicon fine particles and the like are subjected to the coating forming step (S4), the complex forming step (S5), and the negative electrode forming, which will be described later. The process according to the step (S6) is performed.

In the oxide film removing step (S3) of the present embodiment, hydrofluoric acid is brought into contact with the silicon fine particles or the like by immersing the silicon fine particles or the like in a hydrofluoric acid or an aqueous solution of ammonium fluoride. , A step of contacting hydrofluoric acid or an aqueous solution of ammonium fluoride with silicon fine particles or the like by other methods can also be adopted. For example, spraying a hydrofluoric acid aqueous solution on silicon fine particles or the like as in a so-called shower is another aspect that can be adopted.

(4) Coating forming step (S4)
In the present embodiment, the coating forming step (S4) is performed as a preferred embodiment. However, even if this coating forming step (S4) is not performed, at least a part of the effects of the present embodiment can be achieved. Therefore, as described above, after the pulverization step (S2) or the oxide film removing step (S3), the coating forming step (S4) is not performed, and the following (5) complex forming step (S5) is performed. Is another aspect that can be adopted.

In the present embodiment, a coating forming step is performed in which a part or all of the surface of silicon fine particles or the like that has undergone or has not undergone the oxide film removing step (S3) is covered with a carbon film. Therefore, the silicon fine particles and the like that have undergone the coating forming step (S4) of the present embodiment are thicker than the silicon fine particles and the like that are not covered with carbon because at least a part of the surface thereof is covered with carbon. Will increase. Since the carbon of the present embodiment has conductivity, it is possible to form a conductive negative electrode material. Further, for example, by covering silicon fine particles or the like with carbon having a film thickness of several nm to several μm, not only a thin negative electrode can be formed, but also a relatively thick negative electrode can be easily formed. Note that FIG. 3 shows an example TEM of silicon fine particles and / or aggregates or aggregates thereof (partially enlarged view) that have undergone the coating forming step (S4) of the present embodiment. (Transmission electron microscope) image. The crystalline silicon shown in FIG. 3 mainly has a crystal plane orientation (111) (also simply referred to as “Si (111)” or “(111)”; the same applies to other plane orientations). It was observed.

In addition, for example, it can contribute to the relaxation of the internal stress of the negative electrode as a whole by covering the silicon fine particles and the like with carbon, and more microscopically, the relaxation of the internal stress of the individual silicon fine particles and the like. As a result, the production of the lithium ion battery can be facilitated, and the performance of the lithium ion battery (for example, charge / discharge cycle characteristics) can be improved.

Further, by forming the negative electrode material of the lithium ion battery using silicon fine particles or the like whose surface is at least partially covered with carbon, the charge capacity value and the charge capacity value and the charge capacity value are higher than those of the silicon fine particles and the like which are not covered with carbon. It is also possible to increase the discharge capacity value. For example, according to the research by the inventors of the present application, in the case of silicon fine particles not covered with carbon, for example, when the thickness of the negative electrode material is about 30 μm, the charge capacity value and the discharge capacity value are 500 ( It is less than mAh / g). However, by using silicon fine particles whose surface is at least partially covered with carbon, the charge capacity value and the discharge capacity value are more than doubled (typically, about 3 to about 5 times). Can be made to.

By the way, in the coating forming step (S4) of the present embodiment, the means for coating a part or all (in other words, at least a part on the surface) of the surface of silicon fine particles or the like with a carbon film is particularly limited. Not done. For example, a method of covering at least a part of the surface of silicon fine particles or the like 2 with carbon by a thermal CVD method, which is an example of a chemical vapor deposition method, can be adopted. Specifically, by heating the silicon fine particles and the like 2 at an atmosphere containing an organic gas and / or its vapor at about 600 ° C. or higher and about 1200 ° C. or lower, at least a part of the silicon fine particles or the like 2 on the surface. Can be coated with a film of carbon. Therefore, the thermal CVD apparatus, which is an example of the chemical vapor deposition apparatus, is one aspect of the coating forming portion 60 that can be adopted in the coating forming step (S4) of the present embodiment. Examples of materials (or raw materials) that can be used in the thermal CVD method include one or more selected from the group of methane, ethane, acetylene, ethylene, propane, butane, butane, pentane, isobutane, and hexane. Hydrocarbons and / or one or more known aromatic hydrocarbons. By using copper or a copper alloy as a catalyst, acetylene can be thermally decomposed even at about 400 ° C., which can contribute to lowering the treatment temperature.

As described above, typically, at least a part of the surface of the silicon fine particles or the like 2 is formed by thermally decomposing the hydrocarbon gas on or in the vicinity of the heated silicon fine particles or the like 2 and carbonizing the hydrocarbon gas. It can be said that coating with the carbon film realizes an example of an appropriate carbon film in the present embodiment and is excellent in productivity and industriality. A reduced pressure thermal CVD method or a plasma CVD method, which is another example of the chemical vapor deposition method, can also be appropriately adopted.

Further, another example of a method of coating at least a part of the surface of silicon fine particles or the like 2 with a carbon film is as follows. First, a known organic compound (such as a chlorinated polyethylene elastomer) or a mixture of the organic compound and graphite powder is placed in the coating forming portion 60 at least in the cleaning step (S1) and the pulverization step (S1) of the present embodiment. Adheres or adsorbs to silicon fine particles or the like 2 treated by S2). The organic compound is then heated to a thermal decomposition temperature and carbonized to carbonize the organic compound so that at least a portion of the surface is covered with carbon (typically graphene, graphite, and / or amorphous carbon). It is possible to form the broken silicon fine particles and the like 2. It should be noted that the step of firing the silicon fine particles and the like 2 once formed in a nitrogen atmosphere or a hydrogen atmosphere at, for example, 400 ° C. to 1200 ° C. may be additionally and / or performed in advance. This is one aspect of a modified example of the form. From the viewpoint of preventing, suppressing, or removing the formation of an oxide film on the surface of the silicon fine particles 2 with high accuracy, it is preferable to heat the silicon fine particles 2 in a hydrogen atmosphere.

Further, it is another aspect that can be adopted to form silicon fine particles or the like 2 having at least a part on the surface covered with carbon by using other known means. For example, it is also possible to use a carbon film formed by a known carbon black production method (furness method or channel method). The furnace method is a method in which the creosote oil obtained by distilling coal tar is partially burned in a predetermined chamber in a turbulent diffusion state, and then the droplets are water-cooled. Further, the channel method is a method of precipitating carbon by, for example, colliding a flame formed by burning natural gas with a cooling surface of channel steel. However, since a sulfur component derived from petroleum is contained, it is more preferable to adopt the above-mentioned thermal CVD method, which is a method in which such an impurity component is less likely to be mixed. Further, when each of the above methods is adopted, for example, by giving kinetic energy to silicon fine particles or the like by appropriately adopting a known mechanical structure, silicon fine particles or the like 2 and / or agglomerates thereof or Adopting a method of coating at least a part on the surface of the aggregate with a carbon film makes it more homogeneous (for example, on the surface of silicon fine particles and / or agglomerates thereof or the aggregate). This is a preferred embodiment because it enables the formation of a carbon film (with good uniformity in thickness and / or density). More specifically, while rotating the chamber or tube containing the silicon fine particles and the like 2 and / or applying ultrasonic vibration to the silicon fine particles and / or their aggregates or aggregates. Adopting a method of coating at least a part of the surface of silicon fine particles and / or agglomerates or aggregates thereof with a carbon film is to adopt silicon fine particles and / or agglomerates or aggregates thereof. This is a preferred embodiment because it enables a more uniform carbon film to be formed on the surface of an object.

In the first embodiment when the coating forming step (S4) is performed, the carbon (C) when silicon (Si) is 1 for the negative electrode material or the silicon fine particles and the like 2 which play a part of the negative electrode. However, if the weight ratio of carbon (C) when silicon (Si) is 1 is 0.05 or more and less than 0.37, it is stable and can be charged. A lithium ion battery having a high capacity value and a high discharge capacity value can be obtained.

Further, as a result of further detailed analysis by the present inventor, carbon (transmission electron microscope) image shows that carbon (C) has a weight ratio of carbon (C) of 0.1 when silicon (Si) is 1. The film thickness of the portion where C) was attached to silicon (Si) was about 2 nm to about 3 nm. Further, when the weight ratio of carbon (C) is 0.16 when silicon (Si) is 1, the film thickness of the portion where carbon (C) is attached to silicon (Si) is about 5 nm to It was about 10 nm. Further, when the weight ratio of carbon (C) is 0.21 when silicon (Si) is 1, the film thickness of the portion where carbon (C) is attached to silicon (Si) is also about 5 nm to. It was about 10 nm. In addition, when the weight ratio of carbon (C) is 0.37 when silicon (Si) is 1, the film thickness of the portion where carbon (C) is attached to silicon (Si) is about 50 nm. It was about 90 nm. Therefore, if the film thickness of carbon (C) in the portion adhering to silicon (Si) is 1 nm or more and less than 50 nm, particularly if the film thickness is 2 nm or more and 10 nm or less, it is stable and has a charging capacity. A lithium ion battery having a high value and a high discharge capacity value can be obtained.

Further, the charge capacity value and discharge of the lithium ion battery in which at least a part of the surface of the silicon fine particles and / or their aggregates or aggregates is not covered with carbon (that is, the coating formation step (S4) is not performed). It is possible to have a charge capacity value and a discharge capacity value that are twice or more (typically about 3 times) higher when the one that has undergone the coating forming step (S4) is adopted than the capacity value.

(5) Complex formation step (S5)
As described above, after the pulverization step (S2) or the oxide film removing step (S3), the complex forming step (S5) is performed through the coating forming step (S4) or without the coating forming step (S4). ) Is performed. The complex formation step (S5) of the present embodiment is a step of forming a complex containing the graphite and the silicon fine particles 2 by surrounding at least a part of the silicon fine particles 2 with graphite.

Specifically, first, silicon fine particles and the like 2 and graphite (typically flaky graphite or expanded graphite) are introduced into the complex forming portion 70. The flaky graphite or expanded graphite of the present embodiment can be formed by a method disclosed in a known method.

Further, in the present embodiment, since the pulverization step (S2) is performed, very fine aggregates or aggregates of silicon fine particles (silicon fine particles) having a volume distribution having a mode diameter and a median diameter of 30 nm or less are performed. Particles and the like 2) are formed. In addition, the aggregate or aggregate is an aggregate or aggregate of silicon fine particles in a multi-layered petal-like or scaly-folded state. Since such very fine silicon fine particles 2 and the like are adopted, the silicon fine particles and the like 2 are mixed with graphite, and the silicon fine particles and the like 2 are taken into the internal space formed by using graphite. A bead mill machine similar to the bead mill machine used in the crusher 20 can be adopted as an example of the complex forming unit 70 in the case of enclosing it and internalizing it, so to speak, integrating or coalescing it. Another example of the complex forming unit 70 is a group of devices in which a known dry treatment or a known wet treatment is used in combination with a crusher represented by a high-speed rotary impact crusher. However, from the viewpoint of substantially reducing the number of steps, when the silicon fine particles and the like 2 and graphite are combined, the complex forming portion 70 includes only the above-mentioned bead mill machine or at least a composite including the bead mill machine. It is preferable to employ a processing device or a combined processing device including a high-speed rotary impact type crusher.

In particular, scaly silicon fine particles and / or aggregates or aggregates thereof incorporate silicon fine particles and the like 2 into layers having an appropriate distance of graphite (particularly expanded graphite) due to the specificity of the shape. It is advantageous for the composite of graphite and silicon fine particles 2 when graphite and silicon fine particles 2 are introduced into the composite forming portion 70 in order to facilitate the formation of graphite and / or to be easily surrounded by the graphite. be. In addition, adopting scaly silicon fine particles and / or agglomerates or aggregates thereof that have undergone the coating forming step (S4) means that silicon is used between layers having an appropriate distance of graphite (particularly expanded graphite). It is preferable because it is easy to take in fine particles and the like 2 with higher accuracy and / or it is easy to surround the silicon fine particles and the like 2 with the graphite. Further, as described above, from the viewpoint of having a higher charge capacity value and discharge capacity value, scaly silicon fine particles and / or aggregates or aggregates thereof have undergone the coating forming step (S4). Is a preferred embodiment.

By performing the complex forming step (S5), the above-mentioned very fine silicon fine particles and the like 2 having agglomerates or aggregates in a multi-layered petal-like or scaly-like folded state are surrounded by graphite. It can form a broken state. In the present embodiment, it is not always necessary to go through a process (typically, "sphericization") in which the edge portion of the graphite is folded so that the silicon fine particles and the like 2 are taken in by the sheet-shaped graphite. After undergoing such a process, it is also possible to adopt a state in which the silicon fine particles and the like 2 are surrounded by graphite.

(6) Negative electrode forming step (S6)
The manufacturing apparatus 100 for the negative electrode material (or negative electrode) of the lithium ion battery of the present embodiment has been treated by the coating forming step (S4) after the pulverization step (S2) or the oxide film removing step (S3). As the untreated negative electrode material, at least a part of silicon fine particles or the like is surrounded by graphite, and a member (for example, copper foil) constituting a part of the negative electrode is bonded (for example, ammonium carboxyl). It includes a mixing section 80 that mixes methyl cellulose (CMC) and styrene-butadiene rubber (SBR), or ammonium carboxylmethyl cellulose (CMC) and polyvinyl alcohol (PVA)). A negative electrode is formed using the mixture layer formed by the mixing portion 80.

<Other processes>
The silicon fine particles and the like obtained by the following steps (A) to (D) are classified, for example, in order to reduce variations in the number distribution and / or volume distribution of the crystallite diameters of the silicon fine particles and the like. Can be done.
(A) Cleaning step (S1), crushing step (S2), and complex forming step (S5)
(B) Cleaning step (S1), pulverization step (S2), oxide film removing step (S3), and complex forming step (S5).
(C) Cleaning step (S1), pulverization step (S2), coating forming step (S4), and complex forming step (S5).
(D) Cleaning step (S1), pulverization step (S2), oxide film removing step (S3), coating forming step (S4), and complex forming step (S5).

<Analysis results of silicon fine particles and the like obtained in the first embodiment>
1. 1. Analysis of silicon fine particles, etc. by SEM image and TEM image

FIG. 4A is an SEM (scanning electron microscope) image of an example of silicon fine particles and / or aggregates or aggregates thereof after the pulverization step (S2) of the first embodiment. Further, FIG. 4B is a diagram showing an SEM image of an example of enlarged silicon fine particles and / or aggregates or aggregates thereof after the pulverization step (S2) of the first embodiment. In addition, FIG. 4C is a diagram showing (a) an SEM image of another example of aggregates or aggregates of silicon fine particles in the first embodiment, and (b) a partially enlarged view of (a). be. In addition, FIG. 5 is a diagram showing a transmission electron microscope (TEM) image of the silicon fine particles of the first embodiment.

As shown in FIG. 4A, not only individual silicon fine particles but also silicon fine particles shown in Y1 and Y2 and / or agglomerates or aggregates thereof were confirmed. Very interestingly, when analyzed in more detail, as shown in FIG. 4B and the Z portion of FIGS. 4C (a) and 4C (b), the silicon fine particles or their agglomerates are, so to speak, thin layered silicon fine particles. It was confirmed that the particles were aggregates or aggregates in a multi-layered petal-like or scaly-like folded state. If observed in more detail, for example, the range of length (major axis) when the width (minor axis) of one or a group of scaly silicon fine particles is 1, is 3.3 to 12.9. there were.

In addition, another interesting finding was obtained from the TEM image shown in FIG. 5 focusing on individual silicon fine particles and the like. Specifically, it was confirmed that the individual silicon fine particles and the like indicated by the region surrounded by the white line in FIG. 5 are crystalline, that is, single crystal silicon. In addition, it was confirmed that at least a part of the silicon fine particles and the like were amorphous polygonal crystallites having a size of about 2 nm to about 10 nm in a cross-sectional view. In FIG. 5, the plane orientation of the crystal is shown in each region surrounded by the white line.

2. Analysis of crystallite diameter distribution of silicon fine particles or the like by X-ray diffraction method FIG. 6 shows (a) crystallites in the number distribution with respect to the crystallite diameter of the silicon fine particles or the like of the first embodiment in the Si (111) direction. It is a graph which shows the diameter distribution and (b) the crystallite diameter distribution in the volume distribution. FIG. 6 shows the results obtained by analyzing the crystallite diameter distribution of silicon fine particles and the like after the pulverization step (S2) by using an X-ray diffraction method. In both FIGS. 6 (a) and 6 (b), the horizontal axis represents the crystallite diameter (nm) and the vertical axis represents the frequency.

From the results of FIGS. 6 (a) and 6 (b), in the number distribution, the mode diameter was 1.6 nm and the median diameter (50% crystallite diameter) was 2.6 nm. In terms of volume distribution, the mode diameter was 6.3 nm and the median diameter was 9.9 nm. Therefore, in the number distribution, it was confirmed that both the mode diameter and the median diameter were 5 nm or less, and more specifically, a value of 3 nm or less was realized. It is worth noting that in the volume distribution, it was confirmed that both the mode diameter and the median diameter were at least 50 nm or less, particularly 30 nm or less, and more narrowly 20 nm or less. Further, in FIG. 6, it was confirmed that an extremely small value of 10 nm or less was realized.

From the results of FIGS. 6 (a) and 6 (b), the silicon fine particles and the like obtained after the pulverization step (S2) using the bead mill method have an average crystallite diameter of about 20 nm or less, more specifically, It was confirmed that it was about 9.8 nm, which realized 10 nm or less. The crystallite diameter distribution of silicon fine particles and the like after the oxide film removing step (S3) is also substantially the same as in FIG.

Therefore, when the results of FIG. 6 and the results of each of the figures of FIG. 4 are combined and analyzed, at least agglomerates or aggregates such as silicon fine particles after the pulverization step (S2) or the oxide film removing step (S3) are found. It can be said that, so to speak, thin layered silicon fine particles or the like having a major axis of about 100 nm or less are folded into a multi-layer petal shape or a scale shape. Further, as can be seen from FIGS. 5 and 6, the silicon fine particles and the like are mainly composed of crystallites having a major axis of 10 nm or less.

Further, as shown in FIG. 6, it can be seen that the silicon fine particles and the like of the present embodiment include silicon fine particles and the like having a crystallite diameter of 1 nm or less. Interestingly, it was also confirmed that the average crystallite diameter in the volume distribution of the silicon fine particles of the present embodiment is about 10 nm. It can be said that this value is a very small value. Further, as described above, further investigation confirmed that the apparent volume diameter of the silicon fine particles and the like was in the range of about 100 nm or less. In particular, by containing a large number of ultrafine silicon particles having a major axis of 5 nm or less, the charge / discharge cycle characteristics derived by the silicon fine particles used as the negative electrode material of the lithium ion battery described later are improved with higher accuracy. It is something that makes you. Further, since at least a part of the surface of the above-mentioned ultrafine silicon particles is covered with carbon, higher charge capacity value and discharge capacity value, and excellent charge / discharge cycle characteristics can be realized.

3. 3. Analysis of plane orientation of crystallites such as silicon fine particles by X-ray diffraction method FIG. 7 (a) shows silicon fine particles and / or aggregates or aggregates thereof before the crushing step (S2) of the first embodiment. It is the result of analyzing the result (P) of the X-ray diffraction measurement and the result (Q) of the X-ray diffraction measurement of silicon fine particles and / or their aggregates or aggregates after the pulverization step (S2) in a wide angle range. .. Further, FIG. 7B is an enlargement of a part of the result (P) of FIG. 7A, and the silicon fine particles and / or their aggregation after the crushing step (S2) of the first embodiment. It is the result (R) which analyzed the result of the X-ray diffraction measurement of an object or an aggregate in a limited angle range. The peak intensities of the C (002) plane and the C (003) plane shown in FIG. 7 (b) are such that graphite fine particles of about 1 wt% to about 3 wt% are silicon fine particles or silicon fine particles. It indicates that it is contained in an agglomerate or an aggregate. As an example, the size of the graphite fine particles on the C (002) plane is about 50 nm or less, more specifically, about 35 nm, and the size of the graphite fine particles on the C (003) plane is about 100 nm. Hereinafter, more specifically, it was about 75 nm.

As shown in FIGS. 7 (a) and 7 (b), compared with the diffraction peak attributable to the crystal plane (111) of Si near 2θ = 28.4 ° before the pulverization step (S2) of the first embodiment. It was confirmed that the diffraction peak attributable to Si (111) after the pulverization step (S2) had a large half-value width. The average crystallite diameter calculated using Scherrer's equation from the half width of the Si (111) peak after the pulverization step (S2) was 9.8 nm. Also, very interestingly, the intensity of the diffraction peak attributed to Si (111) near 2θ = 28.4 ° after the pulverization step (S2) is the intensity of other diffraction peaks (for example, Si (220) or Si). It became clear that it was larger than the peak intensity of (311). The arrangement interval of Si (111) in the crystal lattice of the silicon fine particles after the pulverization step (S2) is 0.31 nm (3.1 Å) as shown in FIG.

Based on the above analysis results, as for the silicon fine particles and the like after the crushing step (S2) of the present embodiment, the crystalline silicon fine particles and the like whose plane orientation is (111) are mainly multi-layer petals or It can be said that it is an agglomerate or an aggregate in a state where it is folded multiple times in a scaly shape.

Then, by using the silicon fine particles and / or their aggregates or aggregates after the crushing step (S2) or the oxide film removing step (S3) of the present embodiment as a part of the negative electrode material of the lithium ion battery, lithium is used. ^{When lithium ions (Li +} ) ionized from the positive electrode material of an ion battery reach the negative electrode, the lithium ions (Li ⁺ ) are agglomerates or aggregates in a state in which multiple layers of lithium ions (Li +) are folded in a multi-layered petal shape or a scale shape. It is possible to achieve a unique effect that it is easy to enter and exit the fold gap.

In addition, in the present embodiment, graphite surrounds at least a part of the agglomerates or aggregates of the silicon fine particles in the state of being folded into the above-mentioned multi-layer petals or scales. Therefore, the presence of the aggregate or the aggregate in a multi-layered petal-like or scaly-like folded state provides a negative electrode material or a negative electrode in which lithium ions are easily stored and released. In addition, coupled with the peculiarities of the multi-layered petal-like or scaly shape of the aggregate or aggregate, they are surrounded by graphite, thereby suppressing the degree of freedom of the aggregate or the aggregate to some extent. This leads to an increase in the cooperation between graphite and the aggregate or the aggregate, and thus it is possible to realize a high degree of stability in the moving state of lithium ions. As a result, by adopting this negative electrode material, it is possible to realize a lithium ion battery in which the charge / discharge capacity does not change much even if charging / discharging is repeated, in other words, the charging / discharging cycle characteristics are good. Alternatively, an increase in charge / discharge capacity can be realized.

<Modified example of the first embodiment>
In the first embodiment, silicon chips and the like (more specifically, crystalline silicon chips or cutting chips) obtained as a result of performing only the cleaning step (S1) are crushed into a crushing step (S2). ) Is performed by the complex forming step (S5) using the complex forming unit 70 as an example, which is one of the modifications that can be adopted. As in the first embodiment, the oxide film removing step (S3) can be performed after the cleaning step (S1). Further, as in the first embodiment, the coating forming step (S4), that is, the coating forming portion 60 for forming carbon covering at least a part on the surface of the above-mentioned chips or the above-mentioned cutting chips is used as an example. The coating forming step used may be performed after the cleaning step (S1) or after the cleaning step (S1) and the oxide film removing step (S3).

In this modification, as described above, graphite surrounds at least a portion of silicon chips and the like obtained only by the cleaning step (S1). Further, in this modification, the silicon chips and the like and graphite (typically, flaky graphite or expanded graphite) are contained in the complex forming portion 70 used in the first embodiment. be introduced. After that, the same treatment as in the complex forming step (S5) of the first embodiment is performed to form a complex in which at least a part of silicon chips and the like is surrounded by graphite.

Even when this modification is adopted, the same or at least a part of the effect of the first embodiment can be achieved.

<Second embodiment>
In the lithium ion battery of the present embodiment, silicon chips or the like according to the following aspects (1) to (3) or silicon fine particles surrounded by graphite are used as the negative electrode material. The configuration other than the negative electrode material is the same as the configuration of the conventional CR2032 type coin cell structure lithium ion battery.
(1) Graphite enclosing at least a part of silicon fine particles and / or agglomerates or aggregates of silicon fine particles in a state of being folded into a multi-layer petal shape or a scale shape.
(2) In (1), at least a part of the surface of silicon fine particles and / or the aggregate or the aggregate is covered with carbon.
(3) Graphite surrounds at least a part of crystalline silicon chips or cutting chips.

FIG. 8 is a schematic configuration diagram of the lithium ion battery 500 of the present embodiment. The lithium ion battery 500 of the present embodiment has a negative electrode 512 electrically connected to the negative electrode material and the negative electrode material 514 and a positive electrode electrically connected to the positive electrode material and the positive electrode material 518 in the container 510 of the CR2032 type coin cell. 516, a separator 520 that electronically insulates the negative electrode material and the negative electrode material 514, and the positive electrode material and the positive electrode material 518, and an electrolytic solution 530 are provided. Further, the lithium ion battery 500 of the present embodiment has an external circuit provided with a power supply 540 and a resistor 550 connected to a negative electrode 512 and a positive electrode 516 in order to realize charging / discharging.

The method for manufacturing the lithium ion battery 500 of the present embodiment is as follows.

Regarding the method for producing the negative electrode, first, at least a part of the silicon fine particles or the like produced in the first embodiment is surrounded by graphite, or at least a part of the surface of the silicon fine particles is covered with carbon. About 0.3 g of a material in which at least a part of the particles is surrounded by graphite (hereinafter, collectively referred to as “negative electrode active material”) is a 1 wt% CMC binder aqueous solution, an SBR binder aqueous dispersion (manufactured by JSR Co., Ltd., TRD2001). ) In an approximately 10 mL (milliliter) solution.

In the present embodiment, the dry weight ratio is 67: 11: 13: 9 or 50:25: 20: 5 in the order of carbon black, CMC binder aqueous solution, and SBR binder aqueous dispersion, such as silicon fine particles. To mix. Further, in one modification of the present embodiment, the dry weight ratio is 50:25:20: 5 in the order of carbon black, carbon black, CMC binder aqueous solution, and PVA binder aqueous dispersion. do.

Next, the slurry mixed and prepared using an agate mortar was placed on one surface of a copper foil having a thickness of 15 μm and about 9 cm (length) × 10 cm (horizontal) so as to have a thickness of about 30 μm to about 200 μm after drying. After coating on a hot plate, it is dried in the air at 80 ° C. for about 1 hour. Then, the above-mentioned copper foil is punched together with the dried slurry into a circle having a diameter of 11.3 mm corresponding to the battery standard CR2032 type coin cell to form a working electrode. After measuring the weight of the working electrode, the product which has been dried again by vacuum heating at 120 ° C. for 6 hours in a glow box is attached to the inner surface of the negative electrode 512 made of copper foil to obtain the present embodiment. The negative electrode is manufactured.

Next, as for the positive electrode, in order to evaluate the characteristics of the negative electrode material using a lithium ion battery having a half-cell structure, a lithium substrate punched into a circle with a diameter of 13 mm was adopted as the positive electrode 516. As the positive electrode of the lithium ion battery, a known positive electrode can be used instead of the positive electrode 516 described above.

Further, the separator 520 of the present embodiment is a porous polyprolene sheet. In addition, the electrolytic solution 530 of the present embodiment contains 1 mol of lithium hexafluorophosphate (1 L) in a solvent (1 L) in which ethylene carbonate (EC) / diethyl carbonate (DEC) is mixed at a volume ratio of 1/1. An electrolytic solution in which LiPF ₆ ) is dissolved, or a solution obtained by adding fluoroethylene carbonate (FEC) to the electrolytic solution, and injecting an amount within an amount that satisfies the internal volume (about 1 mL) of the CR2032 type coin cell. be.

The above-mentioned positive electrode material and positive electrode material 518, positive electrode 516, negative electrode material and negative electrode material 514, negative electrode 512, separator 520 and electrolytic solution 530 are arranged in the container 510 of the CR2032 type coin cell. Then, in a glove box having an argon atmosphere, each component of the separator 520 and the electrolytic solution 530 is sealed in the container 510 in a state where the positive electrode 516 and the negative electrode 512 of the outer frame of the coin cell are insulated from each other. As a result, a CR2032 type coin cell lithium-ion battery 500 was prototyped.

Examples of the electrolytic solvent constituting the electrolytic solution 530 in the present embodiment include ethylene carbonate (EC), propylene carbonate (PC) (polyprolene sheet) cyclic carbonate, dimethyl carbonate (DMC), and diethyl carbonate (DEC). ), Etc. is a mixed solvent of a chain carbonate organic solvent. Further, a supporting salt such as lithium hexafluorophosphate (LiPF) or lithium tetrafluoroborate (LiBF) can be used by dissolving it in the above-mentioned electrolytic solvent.

By adopting the above-mentioned structure, the presence of the above-mentioned silicon fine particles, or the peculiarity of the multi-layer petal-like or scaly shape of the aggregate or the aggregate, by enclosing them with graphite. The degree of freedom of the above-mentioned silicon fine particles and / or the agglomerates or the aggregates is suppressed to some extent, so that graphite and the silicon fine particles and / or graphite and the agglomerates or the aggregates cooperate with each other. It leads to enhancement. As a result, by adopting this negative electrode material, it is possible to realize a lithium ion battery in which the charge / discharge capacity does not change much even if charging / discharging is repeated, in other words, the charging / discharging cycle characteristics are good. Alternatively, an increase in charge / discharge capacity can be realized.

<Other Embodiments (1)>
By the way, in each of the above-described embodiments, as a starting material, silicon chips formed in the cutting process of a single crystal or polycrystalline silicon block or an ingot are exemplified, but other forms of silicon are used. It is another embodiment that can be adopted by using chips or the like as a starting material. Specifically, silicon chips and the like are not limited to those that are inevitably formed in the cutting process of silicon ingots in the production process of semiconductor products, and preselected crystalline silicon ingots are uniformly formed by a cutting machine. It can also be produced by cutting in or at random. Further, so-called silicon waste materials such as silicon chips and silicon polishing chips, which are usually regarded as waste, can be a starting material for the silicon fine particles of each of the above-described embodiments. Fine debris obtained by crushing debris, waste wafers, etc. may also be included. Further, silicon fine particles using a material such as metallic silicon chips or metallic silicon abrasive chips, or metallic other particulate silicon as a starting material can also be adopted.

<Other Embodiments (2)>
Further, the impurity concentration of the n-type crystalline silicon in each of the above-described embodiments is not particularly limited. Further, not only n-type but also p-type crystalline silicon can be adopted. Further, crystalline silicon, which is an intrinsic semiconductor, can also be adopted as crystalline silicon in each of the above-described embodiments. Since the movement of electrons in the negative electrode material of the lithium ion battery is important, it is more preferable to use crystalline silicon containing n-type impurities. Further, the graphite fine particles of about 1 wt% to about 3 wt% indicated by the peak intensities of the C (002) plane and the C (003) plane shown in FIG. 7 (b) described above are silicon fine particles or the like or silicon fine particles. It should be added that a part or all of these graphites can contribute to the improvement of the conductivity of the negative electrode material because they are contained in the aggregate of the above.

<Other Embodiments (3)>
Further, the silicon fine particles and the like of each of the above-described embodiments and the lithium ion battery provided with the same are not limited to the application to the coin cell type structure introduced in the second embodiment. Therefore, it can be applied to various devices or devices having or using a lithium ion battery having a larger electric capacity than the coin cell type structure.

<Other Embodiments (4)>
Further, as an alternative device to the apparatus 100 for manufacturing the negative electrode material (or negative electrode) of the lithium ion battery shown in FIG. 2 in the first embodiment described above, the negative electrode material (or negative electrode) of the lithium ion battery shown in FIG. 9 The manufacturing apparatus 200 may be adopted. Specifically, from the viewpoint of simplifying the equipment and / or reducing the manufacturing cost, in the negative electrode material (or negative electrode) manufacturing apparatus 200 of the lithium ion battery, silicon chips and the like formed in the silicon cutting process are used. The washing machine 10 for washing the above also serves as a crusher 20 for forming silicon fine particles and the like 2 by crushing the washed silicon chips and the like. Therefore, in the apparatus / method shown in FIG. 9, for example, beads having a relatively large diameter are used in the cleaning step, and beads having a relatively small diameter are used in the crushing step, so that they are used as a negative electrode material for a lithium ion battery. 2 such as silicon fine particles will be obtained. However, in order to obtain the silicon fine particles and the like 2 described in the first embodiment with higher accuracy, the silicon fine particles are used by a bead mill machine after processing using a ball mill machine as in the first embodiment. Etc. 2 is preferably formed.

<Other Embodiments (5)>
Further, according to the analysis by the inventors of the present application, the amount of fluoroethylene carbonate (FEC) added to the electrolytic solution 530 in the second embodiment determines the charge capacity value, the discharge capacity value, and the characteristics of the charge / discharge cycle. It became clear that it could have an impact. This is to form a good (eg, low resistance and / or thin) SEI (solid electrolyte interface) on the surface of the negative electrode material.

The disclosure of each of the above embodiments is provided for the purpose of explaining those embodiments, and is not described for the purpose of limiting the present invention. In addition, modifications that exist within the scope of the invention, including other combinations of each embodiment, are also within the scope of the claims.

The negative electrode material of the lithium ion battery of the present invention and the lithium ion battery provided with the negative material include, for example, various power generation or power storage devices (including small household power storage devices and large power storage systems), smartphones, mobile information terminals, and portable electronic devices. Equipment (mobile phones, portable music players, laptop computers, digital cameras / videos), electric vehicles, hybrid electric vehicles (HEV) or plug-in hybrid electric vehicles (PHEV), motor-powered motorcycles, motors It can be suitable for various devices or devices including motorcycles as a power source, other transportation machines or vehicles, and the like.

1 Chips, etc. 2 Silicon fine particles, etc. 10 Cleaning machine (cleaning and pre-crushing machine)
11 Ball 13a Pot 13b Lid 15 Rotating body 20 Crusher 21 Introduction port 22 Processing room 24 Discharge port 25 Filter 40 Rotary evaporator 50 Oxide film removal tank 55 Hydrofluoric acid or ammonium fluoride aqueous solution 57 Stirrer 58 Centrifugal separator 60 Coating Forming part 70 Composite forming part 80 Mixing part 100 Manufacturing equipment for negative electrode material (or negative electrode) of lithium ion battery 500 Lithium ion battery 510 Container 512 Negative electrode 514 Negative electrode material and negative electrode material 516 Positive electrode 518 Positive electrode material and positive electrode material 520 Separator 530 Electrolyte 540 Power supply 550 Resistance

Claims (15)

Agglomerates or aggregates of the silicon fine particles in which thin layered silicon fine particles are stacked in a scale shape are included.
By incorporating the aggregate or the aggregate between layers of graphite, the graphite surrounds at least a part of the aggregate or the aggregate, and
The silicon fine particles have a volume distribution having a mode diameter and a median diameter of 30 nm or less.
Negative electrode material for lithium-ion batteries. The aggregates or before Symbol collector compound comprises fine particles of 1 wt% to 3 wt% of graphite,
The negative electrode material for the lithium ion battery according to claim 1. The silicon fine particles have a volume distribution in which the mode diameter and the median diameter are 20 nm or less.
The negative electrode material of the lithium ion battery according to claim 1 or 2. The intensity of the diffraction peak attributed to Si (111) near 2θ = 28.4 ° by the X-ray diffraction measurement of the aggregate or the aggregate is larger than the intensity of the other diffraction peaks.
The negative electrode material for a lithium ion battery according to any one of claims 1 to 3. The graphite is expanded graphite.
The negative electrode material for a lithium ion battery according to any one of claims 1 to 4. The negative electrode material for the lithium ion battery according to any one of claims 1 to 5.
Lithium-ion battery. The device including the lithium ion battery according to claim 6. By crushing crystalline silicon, it is an agglomerate or aggregate of thin layered silicon fine particles having a volume distribution having a mode diameter and a median diameter of 30 nm or less, and at least the agglomerates in which the silicon fine particles are stacked in a scale shape. A crushed portion that forms an object or the aggregate, and
A complex containing the graphite and the aggregate or the aggregate by incorporating the aggregate or the aggregate between layers of graphite so that the graphite surrounds at least a part of the aggregate or the aggregate. With a complex forming part that forms a body,
Equipment for manufacturing negative electrode materials for lithium-ion batteries. Further comprising a coating forming portion, which forms carbon covering at least a portion of the aggregate or aggregate on the surface.
The apparatus for manufacturing a negative electrode material for a lithium ion battery according to claim 8. The crystalline silicon is chips or cutting chips machined by a fixed abrasive wire.
The apparatus for manufacturing a negative electrode material of a lithium ion battery according to claim 8 or 9. The crushing unit includes a ball mill machine and a bead mill machine used after the ball mill machine.
The apparatus for manufacturing a negative electrode material for a lithium ion battery according to any one of claims 8 to 10. By crushing crystalline silicon, it is an agglomerate or aggregate of thin layered silicon fine particles having a volume distribution having a mode diameter and a median diameter of 30 nm or less, and at least the agglomerates in which the silicon fine particles are stacked in a scale shape. The crushing step of forming an object or the aggregate, and
By incorporating the aggregate or the aggregate between layers of graphite, the graphite encloses at least a part of the aggregate or the aggregate, thereby containing the graphite and the aggregate or the aggregate. Including a complex forming step of forming a complex,
A method for manufacturing a negative electrode material for a lithium ion battery. Further comprising a coating forming step, which forms carbon covering at least a portion of the agglomerates or aggregates on the surface.
The method for producing a negative electrode material for a lithium ion battery according to claim 12. The crystalline silicon is chips or cutting chips machined by a fixed abrasive wire.
The method for producing a negative electrode material for a lithium ion battery according to claim 12 or 13. In the pulverization step, the crystalline silicon is pulverized by a ball mill and then pulverized by a bead mill to form the agglomerates or aggregates.
The method for producing a negative electrode material for a lithium ion battery according to any one of claims 12 to 14.

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